A motor vehicle window pane can consist of a silicate glass panel, especially a single sheet safety glass pane, which has a transmission reducing layer (TR-layer) (as an antiglare coating) comprising at least one metal, a metal alloy or a metal compound on a free surface of the pane. The TR-layer is applied over the complete surface and the motor vehicle window pane is insertable in a window opening of a metallic motor vehicle body with a peripheral assembly including a piece interposed in the vicinity of an assembly edge strip of the motor vehicle window pane.
By an "assembly-assisting piece" I mean a frame-like component made of rubber or plastic or a suitably located adhesive piece applied as a bead for assembly in the course of the socalled direct gluing.
My invention is especially related to a motor vehicle window pane which is set up for direct gluing, i.e. permits an adhesive bond between the glass and the vehicle body.
It is also related to other motor vehicle window pane constructions which are assembled as a combined safety glass pane made from unprestressed silicate glass panes.
The invention also may make use of a motor vehicle window pane which is made of single-sheet safety glass or in which a silicate glass pane composed of a single-sheet of safety glass is combined with at least one other silicate glass pane.
Usually these motor vehicle window panes are curved. The TR-layer can be a single layer or a multilayer structure; particularly it can have an additional stabilizing layer. The motor vehicle window pane is inserted in the window opening of the motor vehicle body so that the TR-layer is on the surface of the window pane adjacent the motor vehicle interior.
The TR-layer covers the motor vehicle window pane over its entire surface, i.e. to the edge. The motor vehicle window pane can be made from the factory-produced sheet which is coated over an entire surface, and from which the pane is cut out and after that prestressed and/or otherwise processed.
The motor vehicle window pane described above has been proven in regard to transmission reduction and is widely used. Special requirements are demanded of the TR-layer. The TR-layer must be able to withstand the mechanical stresses and strains and the action of corrosion on the window pane in the assembled state.
It must also bear the stresses and strains on thermal prestressing and/or bending in an oxidizing atmosphere without damage. A motor vehicle window pane has proved to be effective with a TR-layer of a structure as described in German Patent Document Nos. 36 11 844 and 36 28 051. My invention is especially related to a motor vehicle window pane in which the TR-layer is applied as described in these documents.
Up to now the known motor vehicle window pane could not be set up simultaneously as an antenna pane and of course neither directly nor indirectly with antenna conductors made of conductive enamel which are burned or fritted in the usual way. The antenna activity has not been satisfactory either for amplitude modulated radio-frequency waves (i.e. radio-frequency waves of long, middle or short wavelengths) or for frequency modulated radiowaves (i.e. radio waves in the ultrashort region).
The conductors tend to interact with the assembly-assisting piece, especially with the adhesive strip in standard use in direct gluing. Actually the known assembly-assisting piece has a comparatively low electrical high frequency resistance because the assembly-assisting pieces usually have a considerable amount of carbon.
Motor vehicle window panes which are impressed with a conductive layer used as a window antenna or with antenna conductors and are used simultaneously as antennas are known.
However other motor vehicle window panes are also known (compare those described in German Pat. No. 34 10 415, and Japanese Patent Document No. 51-30 905).
A conductive layer is provided but an edge strip running peripherally around the glass window pane remains free of the conductive layer.
Usually one normally separates the antenna element for the long/middle/short regions from that of the ultrashort region which additionally is frequently used also as a heating element.
Satisfactory antenna action has hitherto required a comprehensive analysis making use of the Maxwell equations because the conductive layer and/or the antenna conductor of the motor vehicle glass pane with the motor vehicle body interact together electromagnetically.
This intersection leads to particular geometries and arrangements as well as to special features such as the balancing or coupling to the detected electromagnetic energy and the suppression of interfering influences (compare also with the theoretical explanation in German Pat. No. 34 10 415).
However, knowledge of high frequency radio engineering principles can at least lead to optimization. All these measures however give rise to less than satisfactory results.